1. Field of the Invention
The present invention relates to a mobile cargo handling system which includes a vehicle having a driven roller bed, and more particularly relates to such a vehicle provided with a friction drive which is selectively movable between a position in driving engagement with an unpowered bed of rollers for transferring cargo onto or off of said unpowered bed, and a retracted position disposed within the chassis of the vehicle when the vehicle is in position to transfer cargo onto or off of an independently driven bed of rollers.
2. Description of Prior Art
Mobile vehicles for transferring cargo between powered rollers of an aircraft loader and unpowered rollers of terminal storage racks or mobile dollies at an airfield are well known in the art.
One such system is disclosed in Carder et al U.S. Pat. No. 3,506,144 which issued on Apr. 14, 1970. In the Carder et al system a loader is positioned adjacent the cargo opening of an aircraft and includes a driven roller bed that is raised and lowered between the levels of the cargo door of the aircraft and of an unpowered roller bed of a dolly or trailer. Each dolly is, in turn, connected to a tractor which moves the foremost roller of the dolly into frictional engagement with an extractor or friction roller drive. The friction roller drive is journaled on the rear end of the loader and is driven by a reversible hydraulic motor through a chain drive. When the friction roller engages the front roller of the dolly, all of the dolly rollers are driven to move the cargo which is supported on a pallet onto or off of the dolly. However, the Carder et al extractor roller is not retractable within the frame of the loader but is disposed in fixed position of the loader and projects outwardly from the rear end of the loader at all times. Also, the Carder et al extractor is mounted on the loader which is locked in position adjacent the aircraft until it is fully loaded or unloaded, and accordingly is not moved into operative engagement with unpowered rollers on a dolly or unpowered rollers at aircraft storage racks.
McCartney et al U.S. Pat. No. 3,489,300 which issued Jan. 3, 1970 discloses another system for transferring containers between a dolly or trailer and an aircraft loader. This system discloses a transporter with an anti-friction unpowered main roller bed and a pair of forwardly projecting tongues which support a pair of driven rollers that cooperate with another pair of driven rollers near the near end of the transporter. The four driven rollers are raised above the level of the unpowered rollers on the bed of the transporter. The cooperating pallet dolly includes unpowered rollers on its main body and also on spaced tongues which interfit with the transporter tongues. The front of the transporter is lowered to permit the cooperating tongues of the transporter and dolly to be moved into transfer position. The forward end of the transporter is then raised so that the forward drive rollers move above the main roller plane to frictionally engage a pallet thereon and drive the pallet onto or off of the dolly. When the pallet is to be transferred to the powered roller bed of an aircraft roller, the forward end of the transporter is moved into abutting engagement with the chassis of the loader. However, the driven transporter rollers in this system are not retractable and do not engage and drive the unpowered rollers of a dolly or the like but instead must be raised above the plane of the main roller deck so that the two forward rollers directly engage the bottom of the pallet. Also, the driven rollers are very narrow and therefore localize their driving forces to small areas of the pallet or article carried by the transporter.